1. Technical Field
This invention relates generally to internal combustion engines, and more particularly to metallic cylinder head gaskets therefor.
2. Related Art
Metallic gaskets are widely used in internal engine applications to establish a seal between opposing surfaces of a cylinder head and an engine block. The seal is typically created to prevent leakage of fluids such as combustion gases, oil, coolant, and the like. The gaskets are typically constructed from several continuous planar sheets or layers of metal formed with the appropriate openings to accommodate cylinder bores, fluid flow between the cylinder block and engine block and fasteners joining the cylinder block to the engine block. The layers are laminated to provide a resiliently compressible, multi-layer structure. At least one outer layer is typically embossed to define annular beads extending outwardly from the plane of the layer, with the beads being formed to circumvent the cylinder bores. As such, when the cylinder head is fastened to the engine block, the beads are resiliently compressed between the opposing surfaces of the engine block and cylinder head to define sealing surfaces between the beads and the respective surfaces to prevent leakage of the associated fluid or gas.
In application, the ability to establish a seal about the cylinder bore openings can be complicated by varying degrees in which cylinder liners extend above a face surface of the engine block, sometimes referred to as cylinder liner overstand. As the cylinder block is fastened to the engine block, the varying degrees of cylinder liner overstand can result in the beads of the gasket being compressed axially under differing pressures from one another. In addition, if the overstand of an individual cylinder liner is nonuniform, the respective bead can be compressed in a skewed relation to the plane of the gasket and/or in a skewed relation to the remaining beads of the gasket. The difficulty of establishing a reliable seal is further complicated by movement of the individual cylinder liners in use, as is commonly experienced between compression and exhaust strokes of the respective pistons. The sealing difficulty results largely from the beads of the gasket layers being restricted in their ability to float, skew or move axially relative to one another with the individual movements of the cylinder liners. As such, the inability of the beads to follow the movements of the respective cylinder liners generally results in a fluid leak, thereby diminishing the efficiency and useful life of the engine.